AirHint found the following cheapest return flights from Singapore (SIN) to Kathmandu (KTM) in September 2025 (see full year).

Return flights

23 Sep - 17 Oct	IndiGo
23 Sep - 16 Oct	IndiGo
27 Sep - 03 Oct	AirAsia
25 Sep - 05 Oct	IndiGo
22 Sep - 27 Sep	Thai Airways
25 Sep - 01 Oct	Air India
20 Sep - 23 Sep	Air India
23 Sep - 30 Sep	Air India
20 Sep - 23 Sep	Singapore Airlines	direct
23 Sep - 26 Sep	Air India
25 Sep - 12 Oct	Air India
29 Sep - 13 Oct	Air India
26 Sep - 01 Oct	Air India
27 Sep - 10 Oct	Air India
26 Sep - 06 Oct	Air India
26 Sep - 30 Sep	Air India
26 Sep - 30 Sep	Singapore Airlines	direct

Also check the deals for one-way flights from Singapore to Kathmandu in September.

The deals are updated regularly. The prices may go up as tickets are purchased by other travellers. Only the cheapest flights are offered. Select a price to book and secure these cheap prices.

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Cheapest return flights from Singapore to Kathmandu in September from 424€

Return flights